High-temperature Spin Crossover of a Solvent-Free Iron ( II ) Complex with the Linear Hexadentate Ligand [ Fe ( L 2-3-2 Ph ) ] ( AsF 6 ) 2 ( L 2-3-2 Ph = bis [ N-( 1-Phenyl-1 H-1 , 2 , 3-triazol-4-yl ) methylidene-2-aminoethyl ]-1 , 3-propanediamine )

A novel mononuclear iron(II) complex with a linear hexadentate N6 ligand, containing two 1,2,3-triazole moieties, [Fe(L2-3-2Ph)](AsF6)2 (1), was synthesized (L2-3-2Ph = bis[N-(1-Phenyl-1H1,2,3-triazol-4-yl)methylidene-2-aminoethyl]-1,3-propanediamine). Variable-temperature magnetic susceptibility measurements revealed a gradual one-step spin crossover (SCO) between the highspin (HS, S = 2) and low-spin (LS, S = 0) states above room temperature (T1/2 = 468 K). The spin transition was further confirmed by differential scanning calorimetry (DSC). A single-crystal X-ray diffraction study showed that the complex was in the LS state (S = 0) at room temperature (296 K). In the crystal lattice, a three-dimensional (3D) supramolecular network was formed by intermolecular CH⋯π and π–π interactions of neighboring complex cations [Fe(L2-3-2Ph)]2+. AsF6− ions were located interstitially in the 3D network of complex cations, with no solvent-accessible voids. The crystal structure at 448 K (mixture of HS and LS species) was also successfully determined thanks to the thermal stability of the solvent-free crystal.

Magnetochemistry 2018, 4, x FOR PEER REVIEW 2 of 14 complexes showing SCO above 400 K remain scarce [30][31][32][33][34][35].Tong has recently pointed out that ''the main obstacles toward developing high-temperature SCO materials lie in the improper ligand-field strength and poor structural stability caused by the lattice solvents or weak supramolecular interactions'' [31].Developing solvent-free crystals is of particular importance with respect to the availability of the single-crystal X-ray diffraction method in high-temperature regions.Recently, our group has studied N6-coordinated SCO iron(II) compounds bearing 1-R-1H-1,2,3triazole-containing multidentate Schiff-base ligands such as tridentate [33], tetradentate [35,36], and tripodal hexadentate ligands [37].Interestingly, most of these compounds showed SCO behaviors either around RT or at remarkably high temperatures.Thus, this ligand system may generally provide a strong ligand-field strength in inducing RT or high-temperature SCO.We must examine this hypothesis in other 1,2,3-triazole-containing multidentate Schiff-base ligand systems such as bidentate, pentadentate, and linear hexadentate ligands.

Synthesis and Characterization of [Fe(L2-3-2 Ph )](AsF6)2 (1)
The linear hexadentate N6 ligand L2-3-2 Ph was prepared by the 2:1 condensation reaction of 1phenyl-1H-1,2,3-triazole-4-carbaldehyde and N,N'-bis(2-aminoethyl)-1,3-propanediamine in methanol (MeOH).The iron(II) complex 1 was prepared by mixing methanolic solutions of the ligand with FeCl2•4H2O and a MeOH/H2O mixed solution of KAsF6 with a 1:1:2 molar ratio under an inert nitrogen atmosphere at ambient temperature.Dark orange-red block crystals were precipitated in one day.They were stable in the air and showed no efflorescence.The chemical formula of [Fe(L2-3- and crystal structure analysis.These results indicated that no solvent molecules were involved in the crystal.As shown in Figure 1b, during the TG measurement, the initial dark orange-red color of the grinding samples at ambient temperature was unchanged until ~400 K, where it gradually Magnetochemistry 2019, 5, 10 3 of 13 changed to yellow-brown between 400 and 515 K, suggesting the occurrence of SCO above RT.This yellow-brown color of the sample was retained until ~550 K, where it then turned black with an abrupt weight loss, corresponding to degradation.The phase purity of 1 was confirmed by the powder X-ray diffraction (PXRD) pattern compared to the simulated powder diffractogram from the single-crystal X-ray structural data (Figure 2).The infrared spectrum of 1 showed characteristic bands at ~1596 and 702 cm −1 , corresponding to the C=N stretching vibration of the Schiff-base ligand and the AsF 6 − ion, respectively [57,58].
Magnetochemistry 2018, 4, x FOR PEER REVIEW 3 of 14 corresponding to degradation.The phase purity of 1 was confirmed by the powder X-ray diffraction (PXRD) pattern compared to the simulated powder diffractogram from the single-crystal X-ray structural data (Figure 2).The infrared spectrum of 1 showed characteristic bands at ~1596 and 702 cm -1 , corresponding to the C=N stretching vibration of the Schiff-base ligand and the AsF6 − ion, respectively [57,58].corresponding to degradation.The phase purity of 1 was confirmed by the powder X-ray diffraction (PXRD) pattern compared to the simulated powder diffractogram from the single-crystal X-ray structural data (Figure 2).The infrared spectrum of 1 showed characteristic bands at ~1596 and 702 cm -1 , corresponding to the C=N stretching vibration of the Schiff-base ligand and the AsF6 − ion, respectively [57,58].

Magnetic Properties of Complex 1
The magnetic susceptibilities were measured upon heating from 300 to 515 K and subsequent cooling to 300 K at a sweep rate of 1 K min −1 under an applied magnetic field of 1 T using a SQUID magnetometer with a special heating setup.The χ M T versus T plots for the ground sample are shown in Figure 3, demonstrating a complete one-step SCO between HS (S = 2) and LS (S = 0) states above RT, where χ M is the molar magnetic susceptibility, and T is the absolute temperature.The χ M T value was 0.0 cm 3 K mol −1 at 300 K, which was consistent with the theoretical value for a LS Fe II (S = 0) complex, and this χ M T value was almost constant in the temperature region <380 K.After further raising the temperature above 380 K, the χ M T value increased gradually to reach ~3.0 cm 3 K mol −1 at 515 K, which was compatible with the expected value for a HS Fe II (S = 2) complex.The magnetic behaviors were very similar in the heating and cooling modes, indicating the absence of thermal hysteresis.The SCO transition temperature (T 1/2 ) was found to be about 468 K.Although the gradual SCO profile of the present complex 1 was similar to that of the related complex [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 [42], the SCO transition temperature of 1 was considerably higher than that of [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 (T 1/2 = 208 K) by about 260 K, indicating that the 1,2,3-triazole-containing ligand L 2-3-2 Ph gave the ligand field strength, which was stronger than that of the imidazole-containing ligand H 2 L 2-3-2 .

Magnetic Properties of Complex 1
The magnetic susceptibilities were measured upon heating from 300 to 515 K and subsequent cooling to 300 K at a sweep rate of 1 K min -1 under an applied magnetic field of 1 T using a SQUID magnetometer with a special heating setup.The χMT versus T plots for the ground sample are shown in Figure 3, demonstrating a complete one-step SCO between HS (S = 2) and LS (S = 0) states above RT, where χM is the molar magnetic susceptibility, and T is the absolute temperature.The χMT value was 0.0 cm 3 K mol -1 at 300 K, which was consistent with the theoretical value for a LS Fe II (S = 0) complex, and this χMT value was almost constant in the temperature region <380 K.After further raising the temperature above 380 K, the χMT value increased gradually to reach ~3.0 cm 3 K mol -1 at 515 K, which was compatible with the expected value for a HS Fe II (S = 2) complex.The magnetic behaviors were very similar in the heating and cooling modes, indicating the absence of thermal hysteresis.The SCO transition temperature (T1/2) was found to be about 468 K.Although the gradual SCO profile of the present complex 1 was similar to that of the related complex [Fe(H2L 2-3-2 )](ClO4)2 [42], the SCO transition temperature of 1 was considerably higher than that of [Fe(H2L 2-3-2 )](ClO4)2 (T1/2 = 208 K) by about 260 K, indicating that the 1,2,3-triazole-containing ligand L2-3-2 Ph gave the ligand field strength, which was stronger than that of the imidazole-containing ligand H2L 2-3-2 .

Differential Scanning Calorimetry (DSC) of Complex 1
The DSC measurement was also carried out in the 273-518 K temperature range at a sweep rate of 5 K min -1 to investigate the SCO property of 1 in more detail (Figure 4).The DSC curves upon heating and cooling showed endothermic and exothermic peaks at 483 and 481 K, respectively, which were slightly higher than the T1/2 value from the magnetic data.The corresponding enthalpy (ΔH) and entropy (ΔS) variations were ΔH = -21.5/19.1 kJ mol -1 and ΔS = -44.4/39.7 J K -1 mol -1 , respectively, which were comparable with those of typical iron(II) SCO complexes [1,3].

Differential Scanning Calorimetry (DSC) of Complex 1
The DSC measurement was also carried out in the 273-518 K temperature range at a sweep rate of 5 K min −1 to investigate the SCO property of 1 in more detail (Figure 4).The DSC curves upon heating and cooling showed endothermic and exothermic peaks at 483 and 481 K, respectively, which were slightly higher than the T 1/2 value from the magnetic data.The corresponding enthalpy (∆H) and entropy (∆S) variations were ∆H = −21.5/19.1 kJ mol −1 and ∆S = −44.4/39.7 J K −1 mol −1 , respectively, which were comparable with those of typical iron(II) SCO complexes [1,3].

Crystal Structure of Complex 1
The single-crystal X-ray diffraction data for 1 were collected at 296 K (the LS state) and at 448 K (mixture of HS and LS species), where 448 K was the highest temperature limit for our diffractometer.Table 1 shows the crystallographic data, indicating that the cell dimensions at the two temperatures were similar, and no crystallographic phase transition was observed.The cell volume changed from 3506.82(18)Å at 448 K to 3384.98(14)Å at 296 K, corresponding to a volume reduction of 3.4%.This reduction was associated with a partial spin transition, from the mixture of HS and LS states (448 K) to complete LS state (296 K), as observed from the magnetic susceptibility results.Table 2 summarizes the relevant coordination bond lengths and angles, as well as additional structural parameters such as Σ [59], Θ [60], the continuous shape measures (CShMs) S(Oh) [61], and octahedral volume.The unique crystallographic unit consisted of one complex cation [Fe(L2-3-2 Ph )] 2+ and two AsF6 − ions.
Figure 5 shows the structure of the complex cation [Fe(L2-3-2 Ph )] 2+ at 296 K.The Fe II ion was coordinated by N6-donor atoms of the helically arranged linear hexadentate Schiff-base ligand L2-3-2 Ph to give an octahedral coordination environment with Δ or Λ configuration.Although the complex cation depicted in Figure 5 had the Δ configuration, the complex crystallized in a centrosymmetric space group, P21/n, and complex-cations with both isomers coexisted in the crystal to form a racemic crystal.At 296 K, the Fe-N distances were in the range of 1.930(2)-2.062(3)Å.The average Fe-N distance was 1.988 Å, typical for LS Fe II bound to N6 donors.The Fe-N bond distances at 448 K (1.964(4)-2.086(3)Å) were longer than those expected for a LS Fe II complex and shorter than those expected for a HS Fe II complex with a similar N6-donor ligand.It is noteworthy that the coordination bond distance of Fe-Nimine was shorter than that of Fe-Ntriazole and Fe-Namine.The average Fe-N bond length increased from 1.988 Å at 296 K to 2.027 Å at 448 K.The difference of 0.039 Å was considerably smaller than that found between the HS and LS states reported (ca.0.2 Å) for the SCO Fe II complexes with similar N6-donor ligands, indicating the occurrence of a partial spin transition between 296 and 448 K. On the basis of the 0.2 Å typical difference in the average Fe-N bond length between HS and LS Fe II states, about 20% of the iron centers were in the HS state at 448 K.This is roughly comparable to the HS fraction of ~31% at 448 K estimated from the magnetic results (where χMT = 3.0 cm 3 K mol - 1 at 515 K and χMT = 0.0 cm 3 K mol -1 at 300 K were used as the HS and LS limiting values, respectively, and χMT = 0.94 cm 3 K mol -1 at 448 K).The octahedral distortion parameters Σ and Θ, the CShMs of the Fe II centers relative to the ideal octahedron S(Oh), and the octahedral volume increase from 296 K to 448 K all indicated a rearrangement of the N6 coordination environment to a more distorted octahedral geometry upon LS → HS SCO.These results were consistent with the magnetic susceptibility and DSC results.Finally, it should be noted that the Fe-Ntriazole distances of LS 1 at 296 K were shorter than the related Fe-Nimidzole distances of LS [Fe(H2L 2-3-2 )](ClO4)2 at 150 K (2.020(2) Å)

Crystal Structure of Complex 1
The single-crystal X-ray diffraction data for 1 were collected at 296 K (the LS state) and at 448 K (mixture of HS and LS species), where 448 K was the highest temperature limit for our diffractometer.Table 1 shows the crystallographic data, indicating that the cell dimensions at the two temperatures were similar, and no crystallographic phase transition was observed.The cell volume changed from 3506.82(18)Å at 448 K to 3384.98(14)Å at 296 K, corresponding to a volume reduction of 3.4%.This reduction was associated with a partial spin transition, from the mixture of HS and LS states (448 K) to complete LS state (296 K), as observed from the magnetic susceptibility results.Table 2 summarizes the relevant coordination bond lengths and angles, as well as additional structural parameters such as Σ [59], Θ [60], the continuous shape measures (CShMs) S(Oh) [61], and octahedral volume.The unique crystallographic unit consisted of one complex cation [Fe(L 2-3-2 Ph )] 2+ and two AsF 6 − ions.
Figure 5 shows the structure of the complex cation [Fe(L 2-3-2 Ph )] 2+ at 296 K.The Fe II ion was coordinated by N 6 -donor atoms of the helically arranged linear hexadentate Schiff-base ligand L 2-3-2

Ph
to give an octahedral coordination environment with ∆ or Λ configuration.Although the complex cation depicted in Figure 5 had the ∆ configuration, the complex crystallized in a centrosymmetric space group, P2 1 /n, and complex-cations with both isomers coexisted in the crystal to form a racemic crystal.At 296 K, the Fe-N distances were in the range of 1.930(2)-2.062(3)Å.The average Fe-N distance was 1.988 Å, typical for LS Fe II bound to N 6 donors.The Fe-N bond distances at 448 K (1.964(4)-2.086(3)Å) were longer than those expected for a LS Fe II complex and shorter than those expected for a HS Fe II complex with a similar N 6 -donor ligand.It is noteworthy that the coordination bond distance of Fe-N imine was shorter than that of Fe-N triazole and Fe-N amine .The average Fe-N bond length increased from 1.988 Å at 296 K to 2.027 Å at 448 K.The difference of 0.039 Å was considerably smaller than that found between the HS and LS states reported (ca.0.2 Å) for the SCO Fe II complexes with similar N 6 -donor ligands, indicating the occurrence of a partial spin transition between 296 and 448 K. On the basis of the 0.2 Å typical difference in the average Fe-N bond length between HS and LS Fe II states, about 20% of the iron centers were in the HS state at 448 K.This is roughly comparable to the HS fraction of ~31% at 448 K estimated from the magnetic results (where χ M T = 3.0 cm 3 K mol −1 at 515 K and χ M T = 0.0 cm 3 K mol −1 at 300 K were used as the HS and LS limiting values, respectively, and χ M T = 0.94 cm 3 K mol −1 at 448 K).The octahedral distortion parameters Σ and Θ, the CShMs of the Fe II centers relative to the ideal octahedron S(Oh), and the octahedral volume increase from 296 K to 448 K all indicated a rearrangement of the N 6 coordination environment to a more distorted octahedral geometry upon LS → HS SCO.These results were consistent with the magnetic susceptibility and DSC results.Finally, it should be noted that the Fe-N triazole distances of LS 1 at 296 K were shorter than the related Fe-N imidzole distances of LS [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 at 150 K (2.020(2) Å) [42] by about 0.04 Å.Other Fe-N distances were almost similar to those of LS [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 at 150 K (Fe-N imine = 1.919(2)Å and Fe-N amine = 2.052(2) Å), possibly reflecting the stronger ligand field strength of 1 compared to that of [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 .
Figure 6 shows the network structure of 1 at 296 K.As shown in Figure 6, adjacent complex cations [Fe(L 2-3-2 Ph )] 2+ of 1 were connected by three types of intermolecular CH• • • π interactions between C9-H7 imine and C5 Ph i , C14-H17 methylene and Cg1 Ph ii , and C19-H25 triazole and Cg2 Ph iii , with the distances of C9-H7  The overall gradual SCO behavior, with no hysteresis of 1, presumably reflected weak cooperativity between SCO metal sites in the lattice, while the SCO-active cations constructed the 3D supramolecular network through intermolecular CH• • • π and π-π interactions.This may be due to the packing effect with counter anions, which tightly occupy the space of the 3D network.On the basis of the potential energy wells of the HS and LS states in a configurational coordinate diagram, with the metal-ligand distance as the configuration coordinate, the condition for observing a thermal spin transition was that the zero-point energy difference between the two spin states, ∆E • HL = E • HS − E • LS , was on the order of the thermally accessible energy, k B T [1,3].Taking into consideration the previously mentioned weak cooperativity of 1, the introduction of the 1,2,3-triazole moiety into the linear hexadentate ligand, instead of the imidazole group, substantially affected the stabilization of the LS state, corresponding to a shift of the LS potential wells to lower energies.As a result, ∆E • HL increased, and the transition temperature shifted to a higher temperature region in 1.

General
All reagents and solvents were purchased from commercial sources and used for the syntheses without further purification.The compound 1-phenyl-1H-1,2,3-triazole-4-carbaldehyde was prepared according to methods in the literature [36,[63][64][65].Complexation and crystallization of 1 were performed under nitrogen atmosphere using standard Schlenk techniques.Other synthetic procedures were carried out in air.

Physical Measurements
Elemental C, H, and N analyses were performed on a J-Science Lab (Kyoto, Japan) MICRO CORDER JM-10.IR spectra were recorded at RT using a JASCO (Tokyo, Japan) FT/IR 460Plus spectrophotometer with the samples prepared as KBr disks.Thermogravimetric data were collected on a Rigaku (Tokyo, Japan) Thermo plus EVO2 TG-DTA8122 instrument in the temperature range of 26-350 • C (299-623 K) at a rate of 10 K min −1 under a nitrogen atmosphere (200 mL min −1 ).Real-time sample images during thermogravimetric analysis were recorded under an optional direct monitoring system of the TG-DTA instrument.DSC measurements were performed with a Rigaku (Tokyo, Japan) Thermo plus EVO2 DSC8231 instrument over the temperature range of 273-518 K, at a sweep rate of 5 K min −1 under a nitrogen atmosphere (50 mL min −1 ), using aluminum hermetic pans with an empty pan as reference.Magnetic susceptibilities were measured in the temperature range of 300-515 K at a sweep rate of 1 K min −1 under an applied magnetic field of 1 T using a Quantum Design (San Diego, CA, USA) MPMS-7 magnetometer with a special heating setup of a sample space oven option.The sample (4.70 mg) was wrapped in a homemade aluminum foil capsule (14.84 mg), mounted inside a quartz glass tube with a small amount of glass wool filler, and then fixed to the bottom of the standard sample transport rod through a copper wire.Corrections for diamagnetism of the sample were made using Pascal's constants [66,67], and a background correction for the sample holder was applied.Small disturbances were noted in the susceptibility data of higher temperature regions, which were likely from a small amount of samples being measured at high temperatures, and the effects of additional disturbances from using an aluminum foil blank.The PXRD pattern was recorded at RT on polycrystalline powders deposited on a glass plate, using a Mac Science MXP3V diffractometer at Cu Kα (λ = 1.5418Å) radiation operated at 1.8 kW power (40 kV, 45 mA).

Crystallographic Data Collection and Structure Analyses
X-ray diffraction data were collected by a Rigaku (Tokyo, Japan) AFC7R Mercury CCD diffractometer using graphite monochromated Mo Kα radiation (λ = 0.71075 Å) operated at 5 kW power (50 kV, 100 mA).A single crystal was mounted on a glass fiber, and the diffraction data were collected at 296 K. Following the measurement at 296 K, the crystal was then warmed to 448 K, and the subsequent measurements were performed.The temperature of the crystal was maintained at the selected value by means of a Rigaku cooling device, with a nitrogen flow within an accuracy of ± 2 K. Data reductions and empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm (multi-scan method) [68], were performed using the CrysAlis Pro software package (version 1.171.39.46) [69].The structures were solved by the direct method using SIR97 [70] and refined on F 2 data using the full-matrix least-squares algorithm, using SHELXL-2014 [71] with anisotropic displacement parameters for non-hydrogen atoms.Hydrogen atoms were fixed in calculated positions and refined by using a riding model.All calculations were performed by using the Yadokari-XG software package [72].The CShMs of the Fe II centers, relative to the ideal octahedron, was calculated by SHAPE 2.1 [61].The octahedral volumes of the Fe II centers were calculated by OLEX2 [73].CCDC 1,887,351-1,887,352 contains the supplementary crystallographic data for this paper.These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the CCDC (12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44-1223-336033; E-mail: deposit@ccdc.cam.ac.uk).
The LS character and the 3D supramolecular network of the complex cations, via intermolecular CH• • • π and π-π interactions at RT, were confirmed by single-crystal X-ray diffraction studies at 296 K.The mixture of HS and LS species at 448 K was also structurally characterized thanks to the thermal stability of the solvent-free crystal.Surprisingly, the SCO transition temperature of the 1,2,3-triazole-containing complex 1 was considerably higher (by about 260 K) than that of the related imidazole-containing complex [Fe(H 2 L 2-3-2 )](ClO 4 ) 2 (T 1/2 = 208 K) [42].This work reveals the effectiveness of introducing a 1,2,3-triazole moiety into a linear hexadentate N 6 ligand, as well as into tridentate, tetradentate, and tripodal hexadentate N 6 -ligand systems for increasing the spin transition temperature above RT.In addition to the present linear 2-3-2-tetramine backbone, a linear 3-2-3-tetramine system is interesting, since the imidazole-containing complexes [Fe(H 2 L 3-2-3 )]X 2 show light-induced excited spin-state trapping (LIESST) with various counter anions X, such as ClO 4 , PF 6 , AsF 6 , and SbF 6 [40,41,43,44].Based on the present compound 1, synthesis of analogues with other substituents, counter anions, and linear 3,2,3-tetramine backbones are now in progress.Computational and photo-magnetic studies of them are also under way.These studies will contribute towards the discovery of high-temperature and photo-active SCO materials.

Figure 2 .
Figure 2. Experimental powder X-ray diffraction (PXRD) pattern of 1 (black) at room temperature (RT) compared with the simulated pattern from the single crystal X-ray data at 296 K (red).

Figure 2 .
Figure 2. Experimental powder X-ray diffraction (PXRD) pattern of 1 (black) at room temperature (RT) compared with the simulated pattern from the single crystal X-ray data at 296 K (red).

Figure 2 .
Figure 2. Experimental powder X-ray diffraction (PXRD) pattern of 1 (black) at room temperature (RT) compared with the simulated pattern from the single crystal X-ray data at 296 K (red).

Figure 3 .
Figure 3.The magnetic behavior of 1 in the form of χMT vs. T plots.Complex 1 was warmed from 300 to 515 K (filled triangles; red) and then cooled from 515 to 300 K (filled inverted triangles; blue) at a sweep rate of 1 K min -1 .

Figure 3 .
Figure 3.The magnetic behavior of 1 in the form of χ M T vs. T plots.Complex 1 was warmed from 300 to 515 K (filled triangles; red) and then cooled from 515 to 300 K (filled inverted triangles; blue) at a sweep rate of 1 K min −1 .

Figure 4 .
Figure 4. Differential scanning calorimetry (DSC) curves of 1 recorded over the temperature range of 273-518 K in the heating (red) and cooling (blue) modes at a sweep rate of 5 K min -1 .

Figure 4 .
Figure 4. Differential scanning calorimetry (DSC) curves of 1 recorded over the temperature range of 273-518 K in the heating (red) and cooling (blue) modes at a sweep rate of 5 K min −1 .

Figure 5 .
Figure 5. ORTEP drawing of the complex cation [Fe(L2-3-2 Ph )] 2+ of 1 at 296 K with the atom numbering scheme, except for carbon and hydrogen atoms, where the thermal ellipsoids are drawn with a 50% probability level.

Figure 5 .
Figure 5. ORTEP drawing of the complex cation [Fe(L 2-3-2Ph )] 2+ of 1 at 296 K with the atom numbering scheme, except for carbon and hydrogen atoms, where the thermal ellipsoids are drawn with a 50% probability level.

Figure 5 .
Figure 5. ORTEP drawing of the complex cation [Fe(L2-3-2 Ph )] 2+ of 1 at 296 K with the atom numbering scheme, except for carbon and hydrogen atoms, where the thermal ellipsoids are drawn with a 50% probability level.
Magnetochemistry 2018, 4, x FOR PEER REVIEW 8 of 14 • C for 1 h.KAsF6 (0.456 g, 2 mmol) in 6 mL of a mixed solution of MeOH, and H 2 O (2/1 by volume) was added to a solution of Fe II Cl 2 •4H 2 O (0.199 g, 1 mmol) in MeOH (4 mL); the resulting mixture was stirred at RT for 40 min.Both reaction mixtures were filtered and mixed under nitrogen atmosphere.The resulting mixture was allowed to stand for one day at RT, during which the precipitated dark orange-red block crystals were collected by suction filtration.